This invention relates to a method for manufacturing a shoe for a swash-plate type compressor, more particularly, to a method for manufacturing a shoe which is to be inserted between a swash-plate and a ball for transmitting the thrust or motive power from the swash-plate to the piston in relation.
A swash-plate type compressor is used for compressing a gas by means of reciprocating a certain number of pistons, each of which is slidably fitted in a cylinder block, with the help of a rotating swash-plate. The power transmission from the swash-plate to the piston is, in general, carried out through the intermediary of the shoe and the ball. Between the shoe and the swash-plate there is produced, while the compressor is in operation, a severe pressing and sliding, and at the same time, a fairly strong thrust as well as a slide are effected between the shoe and the ball.
As the material for the shoe, aluminum-silicon alloys, copper, copper alloys, etc. have conventionally been employed. Aluminum-silicon alloys are not only weak in resistance to high-speed sliding, high-degree of load, and impact, but also unsatisfactory for their low efficiency in production thereof. On the other hand, copper and copper alloys are defective because they are expensive in the material cost.
A way of manufacturing a shoe, economical and durable, from steel was then attempted. A steel shoe is, however, liable to be seized by the ball or the swash-plate, or abnormally worn while in operation, since both the ball and the swash-plate are generally made of steel, the steel-to-steel contact is responsible for this effect. As a way of partly solving this problem the applicants have invented a method of making a shoe which has a layer of sintered alloy of the copper family formed on the contact surface with the swash-plate, which invention was filed as an application alloted a U.S. Ser. No. 615,888, now U.S. Pat. No. 4,037,552. Regarding the sliding surface between the shoe and the ball, the difficulty previously remained unsolved, no satisfactory technique being found in the prior art. Forming a layer sintered with powdered metal on the slide-contacting surface of the shoe concavity contacting the ball, similar to the contacting surface of the swash-plate, is not only technically difficult because of the spherical configuration of the concavity surface but also extremely expensive in its production cost. The plating of copper or a like metal on the slide-contacting surface with the ball of the shoe concavity, as an alternative method, requires a considerable amount of time and a high cost for obtaining a layer of sufficient thickness capable of preventing exposure of the steel base material to the ball, due to the fast wearing out of the layer.